Your heart pumps blood round your body all day and all night, delivering what every cell needs.
The heart is a muscular pump with four chambers. Arteries carry blood away from the heart, veins carry it back, and tiny capillaries connect them and swap materials with the cells. Blood carries oxygen, nutrients and waste.
Red blood cells carry oxygen. White blood cells fight germs. Platelets help blood clot. The liquid part is plasma. Your pulse is the heartbeat you can feel in an artery, for example at the wrist.
The heart is:
Arteries carry blood:
Veins have valves to:
Capillaries are tiny vessels where:
Red blood cells carry:
White blood cells help to:
A resting heart beats about 70 times a minute.
About how many beats is that in one hour?
Enter an exact answer, without rounding.Which vessel carries blood back to the heart?
Platelets help to:
You can feel your pulse in an:
What happens to your heart rate when you exercise?
The liquid part of blood is:
Every cell needs oxygen. The respiratory system brings air in and sends carbon dioxide out.
Air passes through the nose or mouth, down the trachea (windpipe), into two bronchi, then smaller tubes ending in tiny air sacs called alveoli. The diaphragm and rib muscles move to draw air in and push it out.
In the alveoli, oxygen passes into the blood in nearby capillaries and carbon dioxide passes out. Cells use oxygen to release energy from food in respiration. Smoking damages the lungs.
The windpipe is also called the:
Gas exchange happens in the:
When you breathe in, your diaphragm:
Which gas passes from the alveoli into the blood?
Compared with inhaled air, exhaled air has more:
Respiration in cells:
A person breathes 15 times each minute.
How many breaths is that in 10 minutes?
Enter an exact answer, without rounding.Which organ system brings oxygen into the body?
The tiny air sacs in the lungs are called:
Why are the alveoli good for gas exchange?
Smoking is harmful because it:
When you breathe out, your diaphragm:
Some changes can be undone; others make brand new substances that cannot easily be turned back.
In a reversible change no new substance is made, so it can be undone. Melting, freezing, evaporating, condensing and dissolving are reversible.
In an irreversible change (a chemical reaction) one or more new substances form. Signs are a colour change, gas given off, heat or light, a new smell, a solid forming. Burning, baking, rusting and cooking an egg are irreversible.
Which change is reversible?
Which change is irreversible?
Which is a sign of a chemical reaction?
Rusting is a:
Dissolving salt in water is:
Baking a cake is irreversible because:
Which of these is a reversible change?
A chemical reaction always makes:
Vinegar and baking soda fizz because:
Which is NOT a sign of a chemical change?
Which change happens when milk goes sour?
Mass and weight are different things, even though people often mix them up.
Mass is how much matter is in an object. It is measured in kilograms (kg) and does not change. Weight is the pull of gravity on that mass. It is a force measured in newtons (N).
Gravity is the force that pulls objects towards each other. Bigger masses have a stronger pull. On the Moon gravity is about one sixth of Earth’s, so you weigh less but your mass stays the same. Weight is measured with a newton meter (forcemeter); mass with a balance.
Mass is measured in:
Weight is measured in:
An astronaut on the Moon has:
Which instrument measures weight?
Gravity is:
Weight is a:
Take gravity as 10 N for every kg. An object has a mass of 12 kg.
What is its weight in newtons?
Enter an exact answer, without rounding.Which stays the same wherever you go?
A girl has a mass of 40 kg. Her weight on Earth is about:
Why do objects weigh less on the Moon?
Which statement is correct?
Astronauts seem to float in orbit because:
We need energy for homes, transport and industry. It can come from sources that run out or sources that never do.
Non-renewable sources will run out because they take millions of years to form. Fossil fuels (coal, oil, natural gas) are burned to release energy, but they produce carbon dioxide, which contributes to global warming.
Renewable sources are not used up. They include solar, wind, hydroelectric (water), geothermal, tidal and biomass. They create little pollution, but some depend on the weather.
Which is a fossil fuel?
Which energy source is renewable?
Non-renewable means:
In a hydroelectric power station, moving water turns a:
Burning fossil fuels causes:
A disadvantage of solar energy is that:
Which is a renewable source?
Which source produces no carbon dioxide while generating electricity?
Energy from the Sun was stored in fossil fuels by:
Why do countries want more renewable energy?
When fuel burns, chemical energy changes mostly to:
Scientists plan fair tests, collect data and draw conclusions. At Checkpoint you show these skills.
A fair test changes only one thing. The independent variable is what you change. The dependent variable is what you measure. Control variables are kept the same. Repeat the test to improve reliability.
Record results in a table, then show them on a graph (line graph for continuous data, bar chart for categories). Find the mean of repeats and look for a pattern. Your conclusion answers the question using evidence.
In a fair test you change:
The independent variable is the one you:
The dependent variable is the one you:
A control variable is one that is:
Which is best to show how temperature changes over time?
An anomalous result is one that:
Three repeat times for sugar dissolving were 12 s, 14 s and 13 s.
What is the mean time in seconds?
Enter an exact answer, without rounding.Why repeat an experiment?
A conclusion should:
Which is a control variable in the sugar test?
Which tool would you use to measure 50 mL of water?
Which statement is a prediction?
Questions from every topic in this course. Pick an answer for each one, then hit Check My Answers.
Which part pumps blood around the body?
The liquid part of blood is:
Which gas do we need to breathe in?
When you breathe out, your diaphragm:
A change that can be undone is called:
Which change happens when milk goes sour?
Gravity pulls objects towards the:
Astronauts seem to float in orbit because:
Which energy source will NOT run out?
When fuel burns, chemical energy changes mostly to:
Which of these helps make a test fair?
Which statement is a prediction?