NSC / Matric Skills for Science — practice questions

1. Mixing a strong acid with water releases heat, and heat released too quickly can throw the liquid out of the container. 2. The laboratory rule is fixed: never add water to acid, and always add the acid to water. 3. Pouring water onto acid puts a small mass of water onto a large mass of acid, so the heat is released into a tiny volume. 4. Adding both at once, or adding ice first, gives no control at all over how fast that heat appears. _Source: Siyavula Physical Sciences Grade 12 (Everything Science, CC BY 4.0), Chapter 1: Skills for science_

1. Every measurement carries a small error, so no real data set sits perfectly on one line. 2. Joining the dots would build those errors into the graph and hide the real trend. 3. A best fit line is drawn so that the points are spread fairly evenly on either side of it. 4. That line can then be used to read off further values more accurately than any single point allows. _Source: Siyavula Physical Sciences Grade 12 (Everything Science, CC BY 4.0), Chapter 1: Skills for science_

1. An investigation compares one cause with one effect, so the two must be kept apart by name. 2. The variable the learner sets and changes between readings is the independent variable. 3. The variable that responds to that change, and is then measured, is the dependent variable. 4. A controlled variable is deliberately held constant so that it cannot affect the comparison. 5. Calling it the measured variable describes what is read off, not what was chosen and changed. _Source: Siyavula Physical Sciences Grade 12 (Everything Science, CC BY 4.0), Chapter 1: Skills for science_